How to clean my grandmother's photo frame

I used a dampish soft cloth to take off the surface dust. It's very dull compared to what I recall decades ago. Very heavy. My guess is pot metal with a thin coating of paint. My grandmother's photo has always been in this. Is there a way to clean it further without taking off the finish? My parents were chain smokers, so I suspect it's coated with nicotine as everything else in the house was.

 

Hi Bev,
Try using alcohol on a Q-tip, that is the best thing to remove nicotine staining. If no go the paint is oxidizing and needs new coverage.
Use rubbing alcohol which is 70% or 140 proof or vodka which is usually 50% or 100 proof. Rubbing alcohol does a better job.
greg

 

It even smells like an old ashtray. Ick

I didn't have any alcohol in the house, so I put some vodka in a shot glass and used that. It's working!

 

Hi Bev,
Great! I use it on most metals. By the way it is the only thing that gets nicotine off of mirrors.
greg

 

My mother put a piece of heavy plastic over the picture. The glass must have broken long ago. The plastic is totally saturated and yellow, so I have to get a piece of glass.